Domesheet assembly in a keyboard

ABSTRACT

A domesheet assembly for use with a circuit board in a keyboard. The domesheet assembly has a dome-mounting sheet with a plurality of recesses separated by a plurality of bridging sections. A dome is attached to the upper part of a recess via a bead of glue so that only a small section of the dome is physically connected to the dome-mounting sheet. An air passage is provided between neighboring recesses through the bridging section so as to allow some of the air in a recess to escape to the neighboring recesses when a key is pressed. The dome-mounting sheet is securely attached to a printed wire board or printed circuit board by an adhesive to form a domesheet assembly. The domesheet assembly is hermetically sealed to prevent moisture from reaching under the domes.

FIELD OF THE INVENTION

The present invention relates generally to a keyboard and, in particularly, to a domesheet assembly in a keyboard.

BACKGROUND OF THE INVENTION

A keyboard, such as a Qwerty keyboard for use in a computer system, comprises a printed wire board (PWB), a domesheet and plurality of keys disposed on top of the domesheet. A prior art domesheet is shown in FIG. 1. As shown, the domesheet 20 has a plurality of dome sections 22 separated by flat sections 24. An adhesive layer 30 is applied to the underside of the domesheet 20 so that a dome 40 can be attached to each dome section 22. The domesheet 20 is also attached to a PWB 10 by the adhesive layer 30. The surface curvature of the domes 40 is substantially equal to the surface curvature of the dome sections 22 so that the upper surface of each dome 40 is almost entirely in contact with the underside of a dome section 22.

A prior art keyboard is shown in FIG. 2. As shown, the keyboard 90 has an actuating sheet 70 disposed above the domesheet 20 and a housing 60 for mounting the actuating sheet 70 and the PWB 10 along with the domesheet 20. The actuating sheet 70 has a plurality of recesses 76 separated by supporting sections 74 and each recess 76 has a plunger 80. The supporting sections 74 are generally placed in direct contact to the flat sections 24 of the domesheet 20. Each plunger 80 is located directly above a dome section 22, and a key 72 is located directly above a plunger 80. When a key 72 is pressed, the corresponding plunger 80 pushes the dome section 22 toward the PWB 10, causing the corresponding dome 40 to touch the PWB 10. As known in the art, the PWB has electrically conductive segments 15, 16 under each dome section 22, as shown in FIG. 3, and the dome 40 is electrically conductive so that when the dome 40 is in contact with the PWB, the electrically conductive segments 15, 16 are electrically connected. In FIG. 3, the two segments 15 are electrically connected to each other and are in electrical contact with the dome 40. The illustrated two segments 16 are also electrically connected to each other.

As each dome section 22 contains an amount of air in the space 23 under the dome 40, the dome section 22 is effectively an air bubble above the PWB 10. As shown in FIG. 2, the PWB 10 has a plurality of ventilation holes 12 to allow some of the air in the dome section 22 to escape from the space 23 when the dome section is pushed toward the PWB 10. As such, each dome section 22 acts like an air pump that sucks air into the space 23 through the ventilation hole 12 when the key 72 is released after pressing. With these ventilation holes, moisture can move into the space 23 under the dome sections 22, causing corrosion of the domes 40 and the adhesion between the domes 40 and dome sections 22.

It is thus advantageous and desirable to provide a keyboard wherein the domes are sealed from moisture.

SUMMARY OF THE INVENTION

The present invention uses a dome-mounting sheet having a plurality of recesses separated by a plurality of bridging sections. A dome is attached to the upper part of a recess via a bead of glue so that only a small section of the dome is physically connected to the dome-mounting sheet. An air passage is provided between neighboring recesses through the bridging section so as to allow some of the air in a recess to escape to the neighboring recesses when a key is pressed. The dome-mounting sheet is securely attached to a printed wire board or printed circuit board by an adhesive to form a domesheet assembly. The domesheet assembly is hermetically sealed to prevent moisture from reaching under the domes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a prior art domesheet attached to a PWB.

FIG. 2 is a cross sectional view of a prior art keyboard having an actuating sheet and a plurality of keys disposed above the domesheet.

FIG. 3 is a schematic representation showing the electrical contacts on the PWB under each dome section of the prior art domesheet.

FIG. 4 is a cross sectional view of the domesheet assembly of the present invention attached to a PWB.

FIG. 5 is a schematic representation showing a cross section of the keyboard, according to the present invention.

FIG. 6 is a schematic representation showing the electrical contacts on the PWB under each recess of the dome-mounting sheet, according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The domesheet assembly of the present invention is shown in FIG. 4. As shown, the domesheet assembly 100 comprises a dome-mounting sheet 120 and a printed wire board (PWB) 110, a printed circuit board (PCB) or the like. The dome-mounting sheet 120 has a plurality of recess sections 122 separated by bridging sections 124. An adhesive layer 130 is applied to the bridging sections 124 so as to attach the dome-mounting sheet 120 to the PWB 110. Each recess section 122 has a recess 123 having a surface 125. A dome 140 is attached to the surface 125 of the recess 123 by a bead of adhesive material 150. As shown in FIG. 4, the surface 125 is substantially flat or has a large surface curvature as compared to the surface curvature of the dome 140. As such, only a small section of the upper surface of the dome 140 is physically connected to the dome-mounting sheet 120.

A keyboard, according to the present invention, is shown in FIG. 5. As shown, the keyboard 190 has an actuating sheet 170 disposed above the dome-mounting sheet 120 and a housing 160 for mounting the actuating sheet 170 and the PWB 110 along with the dome-mounting sheet 120. The actuating sheet 170 has a plurality of recesses 176 separated by supporting sections 174. The supporting sections 174 are generally placed in direct contact of the bridging sections 124 of the dome-mounting sheet 120. Each recess 176 has a plunger 180 located directly above a recess section 122 and a key 172 is disposed directly above a plunging section 180. When a key 172 is pressed, the corresponding plunger 180 pushes the recess section 122 downward. Through the bead of adhesive material 150, the dome 140 is caused to contact the PWB 110. The PWB has electrically conductive segments 115, 116 under each recess section 122, as shown in FIG. 6, and the dome 140 is electrically conductive so that when the dome 140 is in contact with the PWB 110, the electrically conductive segments 115, 116 are electrically connected. In FIG. 6, the two conductive segments 115 are electrically connected to each other and are in electrical contact with the dome 140.

The dome-mounting sheet 120, according to the present invention, has a plurality of air channels 112 channeling between adjacent recesses 123. As each recess section 122 contains an amount of air, the recess 123 is effectively an air bubble above the PWB 110. When the recess section 122 is pushed downward by a key 172, the air in the deformed recess 123 is allow to escape to other recesses 123 through the air channels 112. As such, there is no need to provide ventilation holes on the PWB 110. The adhesive layer 130 attaching the dome-mounting sheet 120 to the PWB 110 can provide a hermetic seal to the domes 140 and the adhesive material 150.

The dome-mounting sheet 120 can be made of silicone rubber, for example. The dome-mounting sheet 120 can be securely attached to the PWB 110 with a two-sided adhesive film, for example. The film can be sufficiently stiff to ease the manufacturing process. The dome 140 is basically a section of a spherical shell and can be made of metal or other electrically conductive materials, for example. The bead of adhesive material can be a drop of epoxy glue, for example. Preferably, the bead 150 is sufficiently thick so that the bead itself works as a plunger. As such, the dome 140 is always aligned with this plunger. In contrast, the dome 40 and the plunger 80 in the prior art domesheet 20 may not be always aligned, depending upon the alignment between the actuating sheets 70 and the domesheet 20. Misalignment usually causes loss of tactility.

In the dome-mounting sheet 120 of the present invention, ventilation is arranged between recesses within the domesheet assembly 100, not to the outside. As such, the domesheet assembly 100 is hermetically sealed and moisture penetration under the domes is effectively blocked.

It is possible to design the domes with a long travel (0.15mm to 0.4mm, for example). Long travel of keys improves tactility and ergonomics of the keyboard.

Although the invention has been described with respect to one or more embodiments thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention. 

1. A domesheet assembly for use with a circuit board, comprising: a dome-mounting sheet having a plurality of recesses separated by a plurality of bridging sections, each recess having a recess surface, the recess surface having a recess surface curvature; and a plurality of domes, each dome having a first surface facing the recess surface and a second surface facing the circuit board, the first surface having a dome surface curvature smaller than the recess surface curvature, wherein the first surface has a top section connected to the recess surface of one of the recesses.
 2. The domesheet assembly of claim 1, wherein each of the recesses has at least an air escaping passageway connected to one or more adjacent recesses.
 3. The domesheet assembly of claim 1, wherein the top section of the first surface is securely attached to the corresponding recess by a layer of adhesive material.
 4. The domesheet assembly of claim 1, wherein the bridging sections are securely attached to the circuit board.
 3. The domesheet assembly of claim 1, wherein the adhesive material comprises a bead, separating the top section of the dome from the recess surface.
 6. The domesheet assembly of claim 1, wherein the circuit board has a plurality of electrically conductive segments under each recess, and wherein at least a part of each dome is electrically conductive so that when a dome is caused to make contact with the circuit board, at least two of the electrically conductive segments are electrically connected.
 7. A keyboard comprising: a circuit board, a domesheet assembly disposed over the circuit board; a plurality of keys disposed over the domesheet assembly; and an actuating sheet disposed between the keys and the domesheet, wherein the domesheet assembly comprises: a dome-mounting sheet having a plurality of recesses separated by a plurality of bridging sections, each recess having a recess surface, the recess surface having a recess surface curvature; and a plurality of domes, each dome having a first surface facing the recess surface and a second surface facing the circuit board, wherein the first surface has a dome surface curvature smaller than the recess surface curvature so that only a top section of the first surface is connected to the recess surface of one of the recesses.
 8. The keyboard of claim 7, wherein the top section of the first surface is connected to the recess surface by an adhesive material.
 9. The keyboard of claim 7, wherein the dome-mounting sheet further comprises a plurality of channels for providing air passageways between the recesses so as to allow air in the recesses to move between the recesses.
 10. The keyboard of claim 7, wherein the bridging sections are securely attached to the circuit board by an adhesive material.
 11. The keyboard of claim 8, wherein the adhesive material comprises a bead, separating the top section of the dome from the recess surface.
 12. The keyboard of claim 7, wherein the circuit board has a plurality of electrically conductive segments under each recess, and wherein at least a part of each dome is electrically conductive so that when a key is pressed to cause a dome to make contact with the circuit board, at least two of the electrically conductive segments are electrically connected.
 13. A method to improve tactility and protection of a keyboard, the keyboard comprising: a circuit board, a domesheet assembly disposed over the circuit board; a plurality of keys disposed over the domesheet assembly; and an actuating sheet disposed between the keys and the domesheet, wherein the domesheet assembly comprises: a dome-mounting sheet having a plurality of recesses separated by a plurality of bridging sections, each recess having a recess surface, and a plurality of domes, each dome having a first surface facing the recess surface and a second surface facing the circuit board, wherein the first surface has a dome surface curvature, said method comprising: shaping the recess surface such that the recess surface curvature is greater than the dome surface curvature; and securing the first surface of a dome to a part of the corresponding recess surface such that only a top section of the first surface is connected to the recess.
 14. The method of claim 13, wherein the top section of the first surface of the dome is connected to the recess by a bead of adhesive material so that when a key is pressed, the key causes a dome to make contact with the circuit board through the actuating sheet and through the bead.
 15. The method of claim 13, wherein the dome-mounting sheet further comprises a plurality of channels for providing air passageways between the recesses so as to allow air in the recesses to move between the recesses. 